Method of producing refractory metals



p 1811956 c. H. WINTER, JR 7 2,763,542

METHOD OF PRODUCING REFRACTORY METALS Filed March 5, 1951 2 Sheets-Sheet 1 IN V EN TOR.

ATTORNEY.

P 1956 c. H. WINTER, JR 2,763,542

METHOD OF PRODUCING REFRACTORY METALS Filed March 5, 1951 2 Sheets-Sheet 2 IN V EN TOR.

A TTORNE Y.

United States Patent METHOD OF PRODUCING REFRACTORY METALS Charles H. Winter, J12, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Application March 5, 1951, Serial No. 213,879 9 Claims. (Cl. 75-84.5)

This invention relates to the production of metals, particularly titanium, in a relatively high state of purity. More specifically, it relates to improved methods and means for obtaining such metals, through reduction of a volatile halide, especially a chloride, of the metal with a metallic reducing agent such as magnesium.

Titanium or other metal preparation by reduction of their corresponding halides with a metal reducing agent is well known. For example, titanium tetrachloride can be reacted at elevated temperatures with magnesium or other strong reducing metals to obtain a sponge metal reaction product from which the titanium or other metal can be thereafter recovered. Examples of prior reduction methods include those disclosed in U. S. Patents 2,148,345 and 2,205,854. Disadvantageously, these procedures are of batch or discontinuous type from which the resulting sponge metal reaction product must be recovered by forcible removal from the reaction chamber to which it invariably strongly adheres. Furthermore, unlike the more common metals, such as iron, lead, copper, etc., titanium is exceedingly difiicult to separate from residual oxygen, and to avoid or minimize oxygen as well as nitrogen contamination, it is necessary in such processes that the reaction be conducted in an oxygenand nitrogenfree environment. This is accomplished by the maintenance of an inert atmosphere of a rare gas (argon, helium, etc.) over the reactants and reaction products. Such rare gas use also enables one to control or moderate the reaction where large excesses of reducing metal are present. Obviously, the high materials cost and operating difiiculties which attend these operations render their large-scale commercial adoption and exploitation unattractive.

It is among the objects of this invention to overcome the above and other disadvantages in prior metal-producing operations, and to provide novel and commercially useful methods and means for attaining these objects. A particular object is to provide a commercially attractive, continuous type method for manufacturing a metal such as titanium in a relatively high state of purity and by a process wherein continuous reactant addition and continuous reaction product withdrawal can be readily and conveniently effected without the attendant disadvantages of prior batch methods wherein lack of desired metal purity, difficulty of operation, and excessively high operating and other costs are encountered. An additional and particular object is to provide a commercial process for obtaining high purity titanium at relatively low cost and without recourse to costly inert gas use. A further specific object is to provide a novel process in which advantageous reductions in raw material cost will be realized by reason of the increased efiiciency and im proved conversion attained in such process. Further objects and advantages of the invention will be apparent from the ensuing description as well as from the accompanying diagrammatic drawings, showing in illustration .into its reaction zone 8. A discharge outlet 12 is pro-.

forms of apparatus in which the invention can be carried out and in which Fig. I is a side-elevational, vertical, sectional view of one form of such apparatus; while Fig. II is a vertical, sectional view of a modified form thereof.

The above and other objects and advantages are realized in this invention which broadly comprises reacting a suitable reducing metal and a metal halide at a temperature in excess of the melting point of the reducing metal and within a closed reactor, effecting said reaction above solid reaction products and while the walls of the reactor are maintained at a temperature below the melting point of the reducing metal halide reaction product and reactant, and withdrawing the resulting metal and metal halide reaction products in solid form from the reactor.

In a more specific and preferred embodiment, the invention comprises reacting within a closed reaction chamber molten magnesium and vaporized titanium tetrachloride -at a temperature in excess of the melting point of magnesium reactant and while the reactants are indirectly supported upon solidified products of reaction, throughout the reaction cooling and maintaining the walls of the reaction chamber at a temperature between the elting point of the magnesium chloride reaction product and the condensation temperature of the titanium tetrachloride, during the reaction continuously or intermittently withdrawing the titanium metal and magnesium chloride reaction products in solid form from said zone and chamber, and recovering said metal component in purified form from the withdrawn products.

Referring to the drawings, and particularly to Fig. I, there is shown a vertical, normally open-ended, cylindrical type of elongated reactor 1 which, when in use, is adapted to be maintained in closed, gas-tight relationship from the atmosphere. The vessel 1 is formed, preferably, of corrosion-resistant metal or alloy relatively inert at elevated temperatures and pressures to the reactants and reaction products employed in or during the reduction. In spacedly disposed, operative association about the side and top wall exterior surfaces of the reactor is a metal jacketing element 2 adapted to form a fluid passage or channel 3 through which channel a liquid or gaseous cooling fluid, especially water, can be continuously charged from a valve-controlled inlet 4 for flow over the exterior of said reactor and ultimate discharge from the channel via a valved outlet 5, whereby the walls of the reactor can be maintained in relatively cool condition and for a purpose to hereinafter appear. A valved inlet mean-s 6 containing a conventional measuring gauge 7 is disposed in the upper, top portion of the reactor through which a metal halide reactant, such as titanium tetrachloride, can be supplied at controlled rates and in the desired amounts directly to a reaction zone 8. A separate, relatively restricted inlet means 9 having an associated neoprene or other form of gland means 10 adapted to prevent air or other undesired atmospheric gas ingress into the system is also provided in the upper portion of the reactor through which, preferably, a solid form of reducing metal reactant 11, such as magnesium, in pellet, slug, stick, or ribbon form, can be forcibly fed at controlled rates to the reactor and directly discharged vided in the bottom of the reactor through which solid reaction products 13 can be continuously or semi-continously withdrawn for purification, separation, and recovery by means of conventional manually or mechanically actuatableretractor rolls 14. A removable covering plate or other suitable form of closure means (not shown) for the cylindrical outlet 12, provided with ex- 7 ternal cooling. means such as coils together with means for effecting the central heating thereof (also not shown) can be associated for releasable engagement with said outletso that the latter canbe closed from. the atmosphere during the start-up period of the reduction operation. A conventional venting element 15, such as a springloaded valve or rupture disc, is also disposed in the upper portion of the reactor, said element being adapted to function as a safety release for the system as well as to provide a suitable outlet through which purging gases can be removed from the reactor prior to commencement of any given reduction operation.

In producing titanium metal in an apparatus such as that described in connection with Fig. I and by reacting, for example, magnesium with titanium tetrachloride vapor, the outlet 12 of the reaction cylinder 1 is first sealed off from the atmosphere by securing thereover a closure element (not shown). Suitable engaging means such as rods or hooks adapted to become imbedded in an ingot to be withdrawn through said outlet are associatedwith the closure plate whereby withdrawal of such ingot upon subsequent removal of the plate will be facilitated'. A. plug of solid anhydrousm-agnesium chloride is then cast to desired depth within the reactor, following which the closure plate is removed and partial withdrawal: of such plug effected for engagement with the retractor gears 14. That portion of the withdrawn plug which remains within the reactor outlet acts as a sealing means for excluding the atmosphere from the interior of the reactor and its reaction zone. Water or other suitable fluid at about 150155 C. is then passed continuously through the channel 3- to preheat the reactor to above the boiling point of TiCh and prevent condensation of the latter. Liquid TiCh is then fed into the reactor via its outlet 6 until air becomes expelled therefrom and a slight above-atmospheric pressure registers on gauge '7. Molten magnesium metal at about 850 C. is then rapidly and initially introduced via reactor inlet 9 which drops onto. the top surface of the solid plug of MgClz remaining in the outlet 12. Upon its introduction the magnesium reacts with the TiCl4 vapor in reaction. zone 8 and, due to the heat of reaction, a sufficiently high (above, say, 700 C.) temperature soon develops to enable subsequent magnesiumintroduction in the form of a solid pellet orplug 11 by forcible injection through inlet 9. and gland 10. Thereafter the operation is rendered continuous by simply supplying the magnesium and TiClr to the reaction chamber in requisite quantities while adjusting the rate of TiCl4 addition to maintain a substantially constant, relatively slight pressure within that chamber. As the reaction proceeds, magnesium chloride collects as a melt 16 in zone 8 and, due to the cooling action of. the jacketingmeans, that salt soon solidifies to form a retractible MgClzTi ingot 13. The slight ingot shrinkage which results from the cooling enables a ready withdrawal of such ingot as it forms through outlet 12 and by means of the retractor mechanism 14. The titanium metal forms as a porous, spongy mass which extends nearly to the reactor side walls with its pores and surfaces beingfilled and covered with the solidified magnesium chloride. As a consequence, suflicient ingot strength is provided to enable the ingot to readily withstand the mechanical stresses to which it is subjected during' its continuous or intermittent withdrawal from the reactor by the retractor mechanism. Upon such withdrawal, its titanium metal content is recovered by conventional purification treatments and the recovered metal is shaped into ingots, briquettes, sheets, or otherwise suitably fabricated or alloyed, as, desired.

To a clearer understanding of the invention, the following specific examples are given, which are merely in illustration but not in limitation of the invention:

7 Example I An apparatus of the type shown in Fig. I was employed. This consisted of a vertical, water-jacketed iron reaction cylinder 10 in diameter provided with separate inlets for magnesium pellets and titanium tetrachloride introduction. The bottom outlet of the cylinder was closed by means of an iron plate containing external cooling coils about its periphery and means for flame heating the central portion of such plate. About 2" of anhydrous MgClz was first placed in the bottom of the cylinder and water under pressure and at about 150 C, was then circulated through the jacketing channel. The central portion of the iron plate member was then heated to melt the solid MgClz plug formed on such central portion. Small amounts of TiClq. were then admitted to the reaction chamber and vented at outlet 15 until all air was purged from the apparatus and a TiCl4 atmosphere was established. Thereupon, the reduction reaction was initiated by forcing a pellet of Mg metal /2" by 3 through the gland 10 and inlet 9 and allowing it to drop onto the pool of molten magnesium chloride maintained in the bottom of the reactor. With this pool at about 850 C., the magnesium metal soon melts and the reaction starts. A constant gauge pressure of about 3 pounds per square inch was maintained on the system by adding sutiicient TiCl4 through the inlet for that reactant. The reaction was maintained by adding magnesium pellets continuously for 30 minutes, during which period 9 pounds of that reactant and 35 pounds of TiCl4 were added during the run. Soon after commencement of the reaction, the bottom plate was cooled and on completion of the reaction the reaction products were allowed to cool to the jacket temperature or below under the TiClr vapor atmosphere. Upon completion of the cooling operation, the bottom plate was removed and the resulting ingot of MgClz containing the titanium product (weighing 44 pounds after correction for initially added MgClz-) was dropped out of the reactor under force of gravity alone and without recourse to any application of additional force into an associated container which had been previously flooded with dry air to prevent MgCl2 moisture pick-up. This ingot was then heated in an inert atmosphere of argon in a suitable vessel to melt its MgClz content, about 3 3 of which was drained away from the remaining titanium sponge. Removal of residual MgClz from such sponge was effected by recourse to conventional vacuum distillation from which 6.3 pounds of titanium metal of 99.7% purity in 94% yield were recovered. The magnesium efiiciency was calculated to be 70%. After melting down to the massive state, the titanium metal exhibited under Vicker testing procedure a hardness number of Example II Employing an apparatus of the type shown in Fig. I having a reaction cylinder 15" in diameter and provided with serrated reactor rolls associated with its bottom outlet for removing at a controlled rate, either continuously or intermittently, solid reaction products from the reactor as well as additional means in association with its reduction metal inlet for adding molten magnesium metal to initiate the reaction, a continuous type of operation for titanium metal production was resorted to. In cornmencing the operation, the bottom of the reactor was closed by securing thereto a removable plate following which anhydrous MgClz Was cast in the bottom of the reactor to a depth of about 5 feet. The cooled MgClz ingot was then drawn down and partially removed from the reactor for engagement with the retractor rolls disposed below said outlet. Water at C. was admitted under pressure to the channel of the jaicketing element surrounding the reactor whereby preheating of the apparatus and prevention of TiCl4 condensation would be had. Liquid TiCl4 Was then fed into the reactor to displace air and provide a gauge pressure of about 5 pounds per square inch. Initiation of the reduction reaction was effected by injecting about 1 pound of molten magnesium at 850 C. onto the top surface of the MgClz casting. The heat of reaction soon developed sutficient temperature within the reaction zone that pellets of solid Mg could be added at a rate of 90 pounds per hour. TiCl4 was admitted at a rate which maintained the indicated gauge pressure. The resulting solid reaction products in ingot form were slowly withdrawn at a steady rate from the reactor and by means of the retractor rolls. This product was cut into sections, treated as in Example I, and recovery of its titanium metal component effected in yields and quality approximating those given in that eX- ample. In the operation just described, the ingot could be withdrawn at a steady, constant speed or lowered from the reactor outlet intermittently. In the latter instance, cleaning of the walls of the reaction chamber takes place to remove loosely adhering sp attered material therefrom and prevention of reactor vapor leakage is more effectively had.

Example III Zirconium metal of 99.5% purity was obtained by repeating the procedures of Example I, except that in the reduction vaporized ZrCl4, from a vaporizer associated with the reactor, was employed as the purging medium and halide reactant. In addition, the upper portion of the reactor walls was maintained at from 340-350 C. during the 30-minute run by passing a heat transfer oil through a separate jacketing element disposed about said portion, while the lower and outlet sections of the reactor were cooled to 150 C. by means of a surrounding water-cooled jacketing element. By regulating the heating of the vaporizer, a small pressure of ZrCla vapor was maintained in the system. During the run, 43 pounds of Z1C14 were employed and a 52-pound MgClz-Zr ingot was produced. 11.8 pounds of pure Zr W'as recovered from this sponge, to effect a 94% yield of highly satisfactory metal product. 1

Although described as applied to certain specific embodiments, the invention is not restricted thereto and many widely different variations can be resorted to without departing from its underlying spirit and scope. Thus, while magnesium comprises a preferred type of reducing metal reactant, since it possesses almost twice the reducing'power per unit weight of other metals such as sodium, and is readily available in relatively pure, large commercial quantities, other reducing metals are also contemplated for employment. For this purpose, any metal can be used which is more electropositive than the titanium or other metal under production and which in aqueous solutions would have electrode potential values of 2.0 or greater, as shown by the electromotive force series on page 1439 of the 30th edition of Handbook of Chemistry and Physics. Such metals desirably vaiford a rapid reaction at the 7501400 C. temperatures normally employed in my reduction process. Furthermore, being more eleetropositive than the metal under production; i. e., the reducing metal will remove substantially all of the halogen from useful halides of such metal, production is assured of by-product halide salts which :are liquid at the indicated or higher reaction temperatures. Additionally, pounds with the metal under production, e. g., titanium, and melt below the indicated maximum reaction temperature. Among examples of contemplated, useful metals of this type, those of magnesium, calcium, barium, strontium, sodium, potassium, or lithium can be mentioned.

While the invention is particularly useful for titanium,

production, other metals, such as zirconium, columbium, hafnium, molybdenum, tantalum, tungsten, etc., can also be produced hereunder and by like reduction of their volatile halides the halogen component of which has an atomic number greater than 9, i. e., chlorine, bromine, or iodine. Of the halides contemplated, the chlorides such metals do not form intermetallic comproduct seals off such open bottom during reduction and the level of the magnesium chloride within the reactor can be maintained relatively constant throughout the operation by controlled withdrawal of the frozen or solidified ingot.

As above indicated, in such titanium metal production the initial reaction between the magnesium and titanium tetrachloride vapor occurs at a temperature around the melting point of the magnesium. In attaining such initiation temperature, various expedients for starting the process can be resorted to. Thus, hot molten magnesium can be added to an atmosphere of titanium tetrachloride vapor or the reactants or reaction vessel can be brought to such temperature by applying external heat to the reactor. In the instance of hot moi-ten magnesium addition, it will be found expedient to shield the inlet port therefor with an inert, preferably rare, gas such as argon or helium during the short starting time which is needed. By such means, premature reaction with the TiClt and resulting blocking of the reducing metal inlet will be prevented. However, addition to the reactor of the .initiatethe desired reaction.

molten metal reducing agent can be accomplished Without resorting to such inert gas use, by careful and rapid injection of the metal into the TiCl4 atmosphere. Such a procedure for starting a batch process is disclosed in Example I above, wherein the magnesium chloride in the bottom of the reactor is melted by the application of local, external heat. This procedure can also be applied to a continuous type of operation by supplying a closely fitting, removable plate element within the reactor and mounting it in such manner that it can be readily withdrawn after the reaction starts to draw down the ingot for engagement with the retractor rolls. In such instances, a suitable central well, container or vessel can be welded or otherwise secured to the closure plate and a suitable heating element associated therewith. The magnesium or other metal to be employed in the starting operation can be placed in this Well and upon a TiClt atmosphere being established within the reactor, the reducing metal can be heated to the desired temperature to In such instance, the first portion of the titanium formed able plate. This, however, will prove advantageous in that a strong bond will exist between the reaction product ingot and said plate which will insure a positive initial withdrawal of the ingot. The resulting small, ironcontaminated portion can be discarded as an insignificant part of the Whole metal producing operation. ln addition, other auxiliary thermal initiation equipment and devices can be resorted to in conjunction with getting the process on stream such as conventional type electrical resistance heaters disposed at the center of the starting MgCl2 casting. This would also contemplate use of an electric arc to be struck against or in the vicinity of the initial portion of the magnesium or other metal employed in the starting-up operation.

Once the initiation temperature is reached, a vigorous exothermic reaction occurs which is self-sustaining and exists as long as the react-ants are brought together within the reaction zone. When an active reaction zone is established, it is then practical and even desirable to continue to add the reactants in relatively cool state, such as to their economical will adhere to the removin cold liquid or solid form. In this manner, part of the excess heat generated as a result of the reaction advantageously will be utilized for bringing the reactants to the necessary reaction temperature.

Throughout the reduction reaction the walls of the reactor, particularly those adjacent the reaction zone where the heat of reaction is liberated and Within which the reactant metal chloride vapor and reducing metal are retained, are cooled externally to maintain them at a temperature below the melting point of the MgClz or other metal halide by-produc-t and above, preferably, the condensation point of the TiCh or other metal chloride reactant. As noted, this can be accomplished by circulating and evaporating water, or other desired, useful coolant or heat transfer fluid, through channel 3 of the jacketing element, and particularly over the upper walls and dome of the reactor. Alternatively, such cooling can be effected by resorting to simple circulation of Water under pressure or by passing a suitable coolant, either as a liquid spray or air blast, at the desired temperature, over or against the external walls or surfaces of the reactor. To assist and promote the desired heat transfer and removal, suitable radial fins or other forms of heatdissipating means can be associated, if desired, with the reactor.

By the term reaction zone, I refer to that portion of the space within the reactor which lies immediately above the reaction products and within which the actual reduction occurs. it is near the surface of the reducing metal in contact with the chloride under reduction which is at or above the minimum reaction temperature. It includes the surfaces of droplets of molten reducing metal entering the chloride reactant atmosphere and the surfaces of the reducing metal as it spreads out to form a pool or become dispersed in the upper layers of the chloride by-product formed on the available surfaces of the metal product. As noted, it is important that this active reaction Zone be maintained out of substantial contact with the internal surfaces of the reactor.

Cooling of the reactor walls is of vital importance and highly advantageous in the invention. Not only does it maintain the active reaction zone out of contact with the reactor surfaces, but the rather large heat of reaction which is thereby removed results in the formation of a retractible ingot composed of sponge-like metal enclosed in a solidified by-product salt which can be readily withdrawn from the reactor and with remarkable case. In prior methods wherein highly heated reactor walls are employed, tenacious adherence of the metal product to such walls takes place and undesired product contamination occurs. So tenacious in fact is this adherence that in the recovery operation the product must be either bored out of the reactor or the vessel itself destroyed. In the present invention, the prevailing conditions :are such that practically no opportunity for corrosive attack on the reactor equipment can take place, even when using TiCla, and formation upon and adherence of the metal product to the reactor walls with consequent alloying and con- Lamination with iron or other metal is effectively prevented. In consequence, as illustrated in the examples, the reactor equipment can be constructed of iron and, if desired, copper or titanium, etc., as well as of various ferrous alloys. The ferrous metals are particularly practical for use since, as noted, no opportunity exists for product contamination with the wall material.

While in its preferred adaptation the magnesium metal reactant is added at the top of the reactor to allow it to fall through a relatively constant atmosphere of titanium tetrachloride to the main reaction zone located at about the center of the surface of a magnesium chloride melt or pool, if desired the metal reactant can be simultaneously introduced with the halide in the form of a suspension of small particles of magnesium in liquid TiCl4. This mode of introduction is particularly useful after the reaction has been initiated. Similarly, TiCl4 addition can be effected, in either gaseous or liquid state, and the reactant addition rates can be widely varied. Preferably, magnesium addition is effected at a rate approximately equal to its rate of consumption. This, obviously, will vary according to the type and size of apparatus used for a given method of metal addition. In instances where the reaction rate is high relative to the rate of heat removal, I prefer to resort to cold metal and liquid TiCl4 additions.

As indicated, the size and shape of the reaction chamber and the conduit from which the solid reaction products are withdrawn can be varied considerably. While I prefer to employ a vertical, cylindrical or conduit type of reactor, such as shown and described, this is merely because of the greater ease of constructingsuch form. In designing a large-size reactor, it will be found expedient,

to facilitate the cooling operation, to increase the ratio of wall surface to internal volume. Also, it will be found that withdrawal of the ingot from the reactor can be effected while such ingot is in partially or completely frozen condition. That is, the ingot, on Withdrawal from the reactor, can comprise a wholly solidified mass or the outer portion thereof can be in afrozen state, as in the form of a shell capable of being retracted while its interior portion is in semi-solid or liquid state. Advantageously, a considerable depth of ingot is maintained below the reaction zone in order to allow for adequate cooling and freezing of the salt, especially throughout the lower portion of the ingot, so that a sufficient supporting base will be provided for the reactants prior to ingot withdrawal. Also, in order to prevent or minimize absorption of atmospheric moisture by the M gClz, I prefer to withdraw and handle the ingot while its skin temperature is at about 160 C. or within a suitable temperature range of from about C. to 500 C.

As indicated, any type of vertical apparatus can be used, as can a relatively long, narrow or elongated type which is inclined from the vertical. Apparatus height is not limited but in practice height will be found to be related to such factors as cooling, product removal, sealing of the reaction zone, and production rate, etc. One useful, modified form of apparatus comprises that shown in Fig. ll of the accompanying drawings. In this modification, the reactor, reaction zone and conduit withdrawal portions of the apparatus are tilted or inclined from the vertical and to an angle ranging from about 45 to about 89. All other parts of the apparatus are substantially the same as those shown in Fig. I.

Referring to Fig. II, there is shown a cylindrical metal type of open-bottomed metal reactor 1 disposed at an angle of about 70 which, like the Fig. I reactor, can be maintained in gas-tight relationship when in use. Disposed in spaced relationship. about the external surfaces of said reactor is a metal jacketing element 2 which forms a suitable channel or passage 3' through which water or other cooling media can be continuously charged from a valve-controlled inlet 4 for flow over the exterior surfaces of the reactor 1, to be ultimately discharged from the passage 3 via a valved outlet 5 after flowing over and cooling the reactor surfaces. 6 is provided in the upper. portion of the reactor, said inlet 6' being provided. with a measuring or pressure gauge 7' whereby a metal halide reactant can be supplied through said inlet to the reaction zone 8 at controlled rates and. in desired quantities. .A separate inlet 9', about which is disposed a suitable stuffing box or gland 10', is provided in the upper portion of the reactor through which a solid reducing metal reactant 11 can be forcibly or otherwise fed at controlled rates to the reactor for direct discharge into its reaction zone 8'.- A discharge outlet 12'.is provided in the lower or bottom portion'of the reactor through which solid reaction products 13 can be continuously or semi-continuously withdrawn by means of the manually or mechanically actuatable retractor rolls 14. A, removable covering plate or other form of closure. means (not shown) can also be provided for A valved inlet the outlet 12 for sealing otf the interior of the reactor 1' during commencement of the reduction operation. A conventional valve type ventin g means 15 is also disposed in the upper portion of the reactor which functions as a safety release mechanism for the system and for eliminating purging gases from the reactor prior to undertaking a reduction operation.

The apparatus of Fig. 11 is operated in the same manner as that described above in connection with the apparatus of Fig. 1, except that its use advantageously affords an increased reaction zone 8' area and reaction capacity, although the cross section of the recovered solid reaction product remains the same. In addition, the periphery of the more or less planar reaction zone is increased to provide increased heat-removing capacity. As the reaction proceeds in zone 8', magnesium chloride will collect as a melt in the zone 16' and, due to reactor wall cooling, will freeze as a solid salt ingot 13 adapted to be readily and continuously withdrawn from the apparatus through the outlet 12 by means of the retractor gears 14' previously brought into engagement with such ingot.

The advantages in design of said Fig. 11 apparatus are several. Since reaction capacity is increased with no increase in the cross sectional area of the ingot product, said product can be removed at a greater linear velocity. This improves and simplifies control of the retractor operation because the normally slow rate of removal is difiicut to regulate. As reactor tilting becomes extreme, the main reaction zone is rendered long and narrow, which permits magnesium addition at several points and from a multiplicity of inlets longitudinally placed above the reaction chamber. The smaller diameter of ingot obtained from a given production rate also insures an easier handling in the subsequent processing to which such ingot is subjected. 7

As in the case of the apparatus of Fig. I, the shape and size of the reaction chamber of the device shown in Fig. II, can be varied, as desired, and with respect to that of its conduit or withdrawal outlet end. Thus, the reaction chamber above the planar reaction zone 8 can be increased vertically or horizontally to provide greater vapor capacity and increase the distance of the reactor walls from the reaction zone center. Obviously, the angle or degree of tilting can be varied, as can the conduit shape, provided constrictions in the conduit which would prevent ease of reaction product withdrawal are avoided.

As already noted, many advantages are afforded in the reactor wall cooled process of this invention. In addition to those mentioned, the use of large amounts of an expensive rare or other type of gas to maintain an inert atmosphere over the reactants and reaction products is dispensed with. .In the present invention, an atmosphere of reactant metal chloride vapor is maintained in the'reac'tion chamber and resort is had to such reactant as a purging gas prior to bringingthe reactor on stream. In addition, the continuous operation herein afforded enables one to operate the apparatus for prolonged periods and without undesired shut-down or opening of the apparatus which would involve air admission. Furthermore, the recoveredmetal product will be found to be exceptionally free from contaminants, especially oxygen and nitrogen. This high degree of purity is reflected in the greater ductility of titanium metal produced under the invention, as evidencedby the desired decrease Vickers Hardness Number over the values exhibited by a metal produced in accordance with prior procedures.

Another, very great advantage which the invention affords over prior methods wherein the reactor is run at relatively high wall temperatures is the much greater production capacity obtained from reactors of corresponding size in titanium metal production. Thus, when resort is had to the contemplated wall cooling and con tinuous removal of solidified reaction products of this invention, the production rate in pounds per hour per unit of cross-sectional area at the reaction zone will be found to desirably increase at least ten-fold. A further advantage, arising as a direct result of the simultaneous addition of equivalent amounts of reactants, is the high utilization of both the magnesium and the reducible metal chloride. This appears to be due to carrying out the reaction in a rather shallow layer resting on the molten by-product magnesium chloride. only a slight excess of magnesium floating on such chloride is continuously exposed to an atmosphere of pure,

which comprises reacting a reducing metal selected from the group consisting of magnesium, calcium, barium, strontium, sodium, potassium and lithium, with a volatile halide of said refractory metal, the halogen component of which has an atomic number greater than 9, effecting the reaction at from about 750-1400 C. within a closed reaction vessel the reaction zone of which is maintained out of contact with the walls of said vessel, during said reaction maintaining a continuous charge of said reducing metal and metal halidereactants in said reaction zone and subjecting the entire wall surfaces of said vessel to external cooling to maintain them at a temperature below the melting point of the reaction by-product halide salt formed and to solidify said salt in said vessel as a solid, retractable ingot containing the refractory metal being produced, withdrawing said ingot from said vessel during the reaction and recovering therefrom its refractory metal component.

2. A process for producing a refractory metal selected from the group consisting of titanium, zirconium, columbium, hafnium, molybdenum, tantalum and tungsten, which comprises reacting a reducing metal selected from the group consisting of magnesium, calcium, barium, strontium, sodium, potassium and lithium, with a volatile chloride of said refractory metal, effecting the reaction at from about 7501400 C. within a closed reaction vessel the reaction zone of which is maintained out of contact with the walls of said vessel, during said reaction maintaining a continuous charge of said reducing metal and metal chloride reactants in said reaction zone and subjecting the entire wall surfaces of said vessel to ex ternal cooling to maintain them at a temperature below the melting point of the reaction by-product chloride salt formed and to solidify said salt in said vessel as a solid, retractable ingot containing the refractory metal being produced, withdrawing said ingot from said vessel during the reaction and recovering therefrom its refractory metal component.

3. A method for titanium metal production which comprises reacting magnesium with a vaporized chloride of titanium at temperatures ranging from about 750-1400 C., effecting said reaction within a closed reaction vessel the reaction zone of which is maintained out of con-. tact with the walls of said vessel, during said reaction maintaining a continuous charge of said magnesium and chloride of titanium reactants in said reaction zone and subjecting the entire wall surfaces of said vessel to external cooling to maintain them at a temperature below the melting point of the reaction by-product magnesium chloride formed and to solidify said by-product in said vessel as a solid, retractable ingot containing the titanium metal being produced, withdrawing said ingot from said reactor during the reaction, and separating, purifying and recovering the titanium metal component from the withdrawn products.

4. A method for zirconium metal production which comprises reacting magnesium with a vaporized chloride When of zirconium at temperatures ranging from about 750,l'400 C.,, effecting .sa'id reaction within a closed re action vessel the reaction zone of which is maintained out of contact with the walls of said vessel, during said reaction maintaining a continuous charge :of said magnesium and chloride of zirconium reactants in said reaction zone :and subjecting the entire wall surface of said vessel to external cooling to maintain them at a temperature below the melting point of the reaction byproduct magnesium chloride formed and to solidify said by-product in said vessel as a solid, retractable ingot containing the zirconium metal being produced, withdrawing said ingot from said reactor during the reaction, and separating, purifying and recovering the zirconium metal component from the withdrawn products.

5. A method for producing titanium metal which comprises reacting at temperatures ranging from 750-1400 C., molten magnesium with vaporized titanium tetrachloride within a closed reaction vessel the reaction zone of which is maintained out of contact with the internal walls of said vessel, during said reaction maintaining a continuous charge of said magnesium and chloride of titanium reactants in said reaction zone and subjecting the entire wall surfaces of said vessel to external cooling to maintain them at a temperature below the melting point of the reaction by-product magnesium chloride formed and to solidify said by-product in said vessel as a solid, retractable ingot containing the titanium metal being produced, withdrawing said ingot from said rcactor during the reaction, and separating, purifying and recovering the titanium metal component from the Withdrawn products.

6. A continuous process for producing titanium metal which comprises introducing magnesium and titanium tetrachloride into a reaction zone of a closed reaction vessel, effecting the reduction of the titanium tetrachloride therein at from about 750-l400 C. while maintaining said zone out of contact with the internal walls of said vessel and supporting the reactants upon the solidified products of reaction, during said reaction continuously charging said magnesium and titanium tetrachloride reactants into said zone and subjecting the entire wall surfaces of said vessel to external cooling to maintain said surfaces at a temperature below the melting point of reaction by-product magnesium chloride formed and to solidify said by-product therein as a solid, retractable ingot containing the titanium metal being produced, continuousely withdrawing said ingot from said vessel during the reaction and recovering therefrom its titanium metal component.

7. A continuous process for producing titanium metal through reduction of titanium tetrachloride with molten magnesium which comprises continuously charging the magnesium reactant into a reaction zone of a closed reaction vessel for reaction therein with titanium tetrachloride vapor at temperatures ranging from 7501400 C., effecting said reduction while maintaining said reaction zone out of contact with the internal walls of said vessel and while supporting the reactants upon solidified products of reaction which form therein, throughout the reaction externally cooling the walls of said vessel to maintain them at a temperature below the melting point of reaction byproduct magnesium chloride which forms and to solidify said by-product as a solid, retractable ingot containing the titanium metal product under production, during the reaction intermittently withdrawing said ingot from said vessel and recovering the titanium metal component from the withdrawn ingot.

8. A method for producing titanium metal which comprises reacting a molten metal reducing agent selected fromthe group consisting of magnesium, calcium, barium, strontium, sodium, potassium and lithium, with vaporized titanium tetrachloride within a reaction zone of a reaction vessel while maintaining said zone out of contact with the internal surfaces of said vessel, during said reaction main-a taining a continuous charge of said molten metal reducing agent and titanium tetrachloride reactants in said reaction zone, effecting the reaction at temperatures rang-.

ing from 750l400 C., while externally cooling the entire wall surfaces of said vessel to maintain said sur-.

faces at a temperature below the freezing point of the metal chloride reaction by-product formed and above about C. to form a solid, retractable ingot in said vessel containing the titanium metal product under production, withdrawing said ingot from said vessel during the reaction and recovering therefrom its titanium metal component in purified state.

9. A continuous process for producing zirconium metal comprising reacting molten magnesium with vaporized zirconium tetrachloride within a reaction zone of a closed reaction vessel while maintaining said zone out of contact with the internal surfaces of said vessel, ctfecting said reaction at a temperature ranging from about 750l400 C. while the reactants are supported within said zone upon solid products of reaction, during the reaction maintaining a continuous charge of said magnesium and zirconium tetrachloride reactants in said zone and throughout the reaction subjecting the entire wall surfaces of said vessel to external cooling, maintaining them at a temperature below the melting 'point of byproduct magnesium chloride formed in the reaction and to solidify said by-product in said vessel as a solid, retractable ingot containing the zirconium metal under production, continuously withdrawing said ingot from said vessel during the reaction and subjecting the same I to separation treatment to recover its zirconium metal content in pure state.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Bureau of Mines Report of Investigations :R. 'I. 45.19, Production of Ductile Titanium at Boulder 'City,Nev. Aug. 1949. Published by Bureau of Mines, Washington, D. C. Entire report 38 pages. (between pages 4'and 5) relied upon.

Journal of Metals, April 1950, pages 634-640.

Pages 6, 9-14 and Fig. 2 

1. A PROCESS FOR PRODUCING A REFRACTORY METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM, COLUMBIUM, HAFNIUM, MOLYBDENUM, TANTALUM AND TUNGSTEN, WHICH COMPRISES REACTING A REDUCING METAL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, CALCIUM, BARIUM, STRONTIUM, SODIUM, POTASSIUM AND LITHIUM, WITH A VOLATILE HALIDE OF SAID REFRACTORY METAL, THE HALOGEN COMPONENT OF WHICH HAS AN ATOMIC NUMBER GREATER THAN 9, EFFECTING THE REACTION AT FROM ABOUT 750-1400* C. WITHIN A CLOSED REACTION VESSEL THE REACTION ZONE OF WHICH IS MAINTAINED OUT OF CONTACT WITH THE WALLS OF SAID VESSEL, DURING SAID REACTION MAINTAINING A CONTINUOUS CHARGE OF SAID REDUCING METAL AND METAL HALIDE REACTANTS IN SAID REACTION ZONE AND SUBJECTING THE ENTIRE WALL SURFACES OF SAID VESSEL TO EXTERNAL COOLING TO MAINTAIN THEM AT A TEMPERATURE BELOW THE MELTING POINT OF THE REACTION BY-PRODUCT HALIDE SALT FORMED AND TO SOLIDIFY SAID SALT IN SAID VESSEL AS A SOLID, RETRACTABLE INGOT CONTAINING THE REFRACTORY METAL BEING PRODUCED, WITHDRAWING SAID INGOT FROM SAID VESSEL DURING THE REACTION AND RECOVERING THEREFROM ITS REFRACTORY METAL COMPONENT. 